As enterprises increasingly deploy applications across wide area networks (WANs), performance and security for applications such as web, web services, e-mail, remote file systems and custom applications becomes important issues. It is difficult to impossible for most developers and architects to write and deploy applications that run efficiently and securely across WANs, because in-depth networking knowledge is required to do so. Most application developers, architects, administrators lack those skills. As a result, applications, while working fine in local area networks, perform poorly over WANs and might introduce security problems. These problems exist both for internal applications which need to run between data centers or remote offices, as well as external applications deployed between business partners.